As is well known, recently, demand for high-speed and large-capacity communication is increased as information communication represented by the Internet has rapidly grown.
The demand also causes expansion of broadband communication with a telecommunication system or an optical communication system utilizing optical fibers.
A digital communication method is adopted in the telecommunication system or the optical communication system, and a digital communication system is realized by transmitting and receiving data in which 1s and 0 s are combined.
Therefore, in the digital communication system, it is important that the pulse signal representing 1 or 0 is transmitted and received as fast as possible with high reliability.
An evaluation test, such as an error rate test, in which predetermined pulse signals are input, is performed in various communication devices constituting the telecommunication system or the optical communication system for realizing the digital communication system.
Accordingly, performance and reliability are ensured in various communication devices constituting the telecommunication system or the optical communication system.
Generally, characteristics of the pulse signal are defined by eye closure (eye opening degree) when an eye pattern is formed.
IEEE (Institute of Electrical and Electronics Engineers) defines the eye closure of the pulse signal used in evaluating various communication devices, and IEEE establishes a standard in which a test with the pulse signal having the defined eye closure is perform as a stress test (for example, see IEEE Draft P802 3ae/D5.0 May 1, 2002 pp. 477-481 FIG. 52-10).
Therefore, in the conventional evaluation system for various communication devices, in order to performed the stress test established by IEEE, a fourth order Bessel-Thomson filter is prepared besides a pulse pattern generator which generates a pulse signal having a desired pulse pattern, and filter characteristics of the fourth order Bessel-Thomson filter are adjusted, which generates the pulse signal having the predetermined eye closure pursuant to the eye closure standard of IEEE.
The stress test for various communication devices is performed with the pulse signal having the established eye closure generated in the above manner.